1. Field of the Invention
The present invention relates to a window regulator for a vehicle door.
2. Description of Related Art
The basic configuration of a double-guide window regulator for a vehicle door includes: a pair of guide rails which are spaced from each other in the forward/rearward (longitudinal) direction of the vehicle and extend in the vertical direction, a pair of slider bases which are supported by the pair of guide rails to be slidably movable up and down along the pair of guide rails, and a pair of windowpane holders which are fixed to the pair of slider bases and hold a windowpane.
In Japanese Unexamined Patent Publication 2011-144627, forming an elongated hole extending in the forward/rearward direction of the vehicle in each of a front and rear pair of slider bases, forming a circular hole in each of the pair of windowpane holders and fastening each slider base and the associated windowpane holder to each other using a fastening member (e.g., a bolt or a pin) through the elongated hole and the circular hole thereof with one of these holes on top of the other are disclosed as a structure for fixing the pair of windowpane holders to the pair of slider bases. Forming the hole in each slider base as an elongated hole extending in the forward/rearward direction of the vehicle makes it possible to adjust the relative position between each slider base and the associated windowpane holder in the forward/rearward direction of the vehicle to thereby accommodate deviations (difference) in pitch (distance) (compensate pitch tolerance) between the pair of slider bases and the pair of windowpane holders in the forward/rearward direction of the vehicle.
Theoretically, it is sufficient to form the aforementioned elongated hole in one of the front and rear pair of slide bases. However, in the above-mentioned Japanese Unexamined Patent Publication 2011-144627, each slider base is provided with the elongated hole to make the pair of slider bases mutually identical in shape. This structure causes an increase in size of the pair of slider bases and requires as a large work space because each slider base and the associated windowpane holder to each other are fastened together using a fastening member (e.g., a bolt or a pin) through the elongated hole and the circular hole thereof with one of these holes aligned with the other. Additionally, collars into which fastening bolts or pins are inserted are each required to be formed into an elongated shape corresponding to the associated elongated hole, which is disadvantageous with regard to both weight and cost. However, it is common general technical knowledge that the fastening hole of each slider base into which a fastening member is inserted is made as an elongated hole to accommodate deviations in pitch between the pair of slider bases and the pair of windowpane holders in the forward/rearward direction of the vehicle, and no other structures to accommodate the deviations in pitch are known in the art. This is the first technical problem to be solved for window regulators having known structure.
On the other hand, in recent years, a double-guide window regulator adopting a resin panel which includes a resin panel on which a pair of guide rails spaced from each other in the forward/rearward direction of the vehicle and extending in the vertical direction are integrally formed; and a pair of slider bases to which a windowpane is fixed and which are supported by the pair of guide rails of the resin panel to be freely slidably movable up and down along the pair of guide rails, has become known in the art. In this type of window regulator, pulleys positioned at the upper and lower ends of each guide rail and a motor assembly positioned at a midpoint between these pulleys are supported on the resin panel in advance to be provided as a sub-assembly to achieve a reduction in number of elements, a reduction in weight and an increase in strength. When the resin panel is mounted to a vehicle door, the pulleys (the resin panel) are mounted to a vehicle door panel (inner panel) by fastening bolts which are inserted into the shaft holes of the pulleys, and a windowpane is fixed to the pair of slider bases.
In this type of double-guide window regulator adopting a resin panel, it has been common general technical knowledge that the pair of slide bases hold the pair of guide rails with no clearance therebetween in the forward/rearward direction of the vehicle (e.g., the pair of slide bases hold the pair of guide rails with guide projections which are formed on the pair of slider bases to come in pressing contact with the pair of guide rails being slightly resiliently deformed).
However, when the pair of guide rails do not have sufficient parallelism due to a low precision of the shape of the resin panel at the time of production thereof or due to thermal expansion or contraction of the resin panel, the surface pressures (sliding loads) at the contact portions between the pair of guide rails and the pair of slider bases increase, which becomes a cause of malfunctioning of the window regulator or noise. If the pair of slider bases are made of resin in particular, the resin materials (the pair of guide rails and the pair of slider bases) move while sliding on each other, which easily causes the problem of malfunctioning or noise to occur. This is a second technical problem that needs to be solved in window regulators having a known structure.